The present invention relates to a veneer lathe and, more particularly, to an improved veneer lathe which cuts off acceptable sheets of veneer even from logs of a relatively poor quality.
A conventional veneer lathe includes a cutting section made up of a knife and a stationary bar which may be replaced partly by a roller bar. A cutting power is transmitted to the cutting section through a chuck adapted to retain a log. One of veneer lathes employing such known technique is disclosed in U.S. Pat. No. 1,641,452. Known veneer lathes of the type described involve drawbacks in various respects as discussed hereinbelow.
First, hard logs, logs having soft cores and logs with splits are not suitable for use and, if used, might cause a chuck to race with the consequent interruption of the power supply and/or result in the breakage of the logs disabling the cutting operation. This is because the supply of the power occurs against a large cutting resistance through the log from centre to cutting surface.
Second, slivers and chips resulting from the cutting of a log are more liable to become wedged in a space adjacent to the cutting edge of the knife if the power is supplied from the core portion. This and other similar troubles occur frequently when logs to be cut have splits and/or rotten spots. The drawbacks described above are detrimental to the rate of operation of a veneer lathe and to the yield as well.
In view of an unavoidable influence of the above problems on the product, logs have hitherto been supplied in two different classes, i.e. logs applicable and unapplicable to the production of plywood. However, the short supply of logs is now so serious that logs of a poor quality must be used. Meanwhile, cutting devices including veneer lathes and slicers constitute an important field in the process of plywood production in which logs are turned into sheets of veneer. The construction of a veneer lathe or any other cutting device dictates the yield since the flow in steps succeeding the cutting step and the quality of the product depend primarily on the grading of logs into applicable and unapplicable classes. A veneer lathe disclosed in U.S. Pat. No. 1,641,452 has a roller bar operatively connected with a drive source through an overrunning clutch as its characteristic feature, but it is not of a design which, as in the present invention described hereinafter, applies a driving force to the outer periphery of a log and, hence, the problems of the prior art still remain unsolved.